The present invention relates to an image forming apparatus such as a copier, printer or facsimile machine. More particularly, the present invention relates to an image forming apparatus equipped with an image forming unit for printing an image on a sheet medium; an image reading unit for reading an image on an original using photoelectric means; and a sheet finishing unit for binding, opening a hole or marking a sheet discharged from the image forming unit. In the image forming apparatus, the sheet finishing unit is arranged above the image forming unit, and the image reading unit is arranged above the sheet finishing unit.
Generally, an image forming apparatus has been known as a copier in which an image reading unit reads an original and an image forming unit produces a copy of the original, or known as a facsimile machine for transmitting an original read by an image reading unit. In recent years, an image forming apparatus has been connected to a computer network as an input/output terminal so that an image forming unit thereof prints data from an external source, or has been used as an input device for sending data read by the image reading unit to a computer.
When the image reading apparatus is used either as a single function device, i.e. a stand-alone unit, or as an I/O terminal in a computer network, it is necessary to perform a finishing process such as binding, opening a hole, or marking on sheets discharged from the image forming unit. The present invention relates to an image forming unit equipped with a sheet finishing unit for automatically finishing sheets.
As business machines such as computers have become compact, there has been a growing demand for an image forming apparatus equipped with an image forming unit, sheet finishing unit and image reading unit to be compact and lower cost as well as capable of handling a variety of sheet media with small to large sizes. There have been proposed and widely used conventional image forming devices in which a sheet finishing unit is arranged above an image forming unit, and an image reading unit is arranged above the sheet finishing unit for making the device small and saving a space.
As shown in FIG. 5, Japanese Patent Publication (Kokai) No. 2002-60118 has disclosed an apparatus in which a sheet finishing unit 530 is arranged above an image forming unit 510 and an image reading unit 520 is arranged above the sheet finishing unit 530. In the image forming unit 510, similar to a normal printer, a sheet stacked on a sheet cassette 511 is guided to a transfer drum 512 and a latent image formed on a transfer drum 512 is transferred to the sheet according to a signal from an image data processing unit. Then, the sheet is transported through a fixer 515, and is discharged through a discharge path 514. The sheet finishing unit 530 is arranged at an edge of an outlet of the discharge path 514 so that the stapling apparatus 532 staples the sheet stacked on the discharge stacker 531.
The image reading unit 520 is arranged above the sheet finishing unit, so that a carriage 524 moves from left to right for reading an original set on a platen glass 522 similar to a conventional scanner. The carriage 524 is provided with a mirror and a light source (not shown). The light source irradiates the original, and the reflected light passes through a lens and is converted into an electrical signal with a photoelectric conversion element such as a CCD 523 to read the image on the original. The electrical signal from the photoelectric conversion element is converted into a digital signal and transmitted to an image data processing unit 513 in the image forming unit 510, so that the image forming unit 510 prints the image.
As shown in FIG. 6, Japanese Patent Publication (Kokai) No. 2002-111935 has disclosed an apparatus in which a sheet finishing unit 630 is arranged above an image forming unit 610, and an image reading unit 620 is arranged above the sheet finishing unit 630. A sheet is transported from a sheet supply cassette 611, and stored on a first discharge stacker 632 after a transfer drum 612 forms an image on the sheet. When a finishing process is instructed, the sheet is stored on a second discharge stacker 631 and a device such as a stapler (not shown) performs a finishing process. The image reading unit 620 moves from left to right for reading the original set on a platen 612.
In the apparatuses disclosed in Japanese Patent Publications (Kokai) No. 2002-60118 and No. 2002-111935, an automatic document feeder can be mounted on the image reading unit as an optional device for feeding the original stacked on the stacker to the discharge stacker through a substantially U-shaped path.
As described above, in the conventional apparatus, the image reading unit is arranged above the sheet finishing unit and the image forming unit is arranged below the sheet finishing unit. In this case, after an image is formed on a sheet in the image forming unit, the sheet is transported in a direction same as a direction that the sheet is transported after being processed in the sheet finishing unit, and same as a direction that the image reading unit scans the sheet. Accordingly, there are the following problems in order to make the apparatus compact.
The sheet normally used has a longitudinal length different from a lateral length (width). When a sheet with the maximum size is transported for image forming, finishing and scanning in a direction same as the longitudinal direction thereof, it is necessary to dispose a function component such as a binding device of the sheet finishing unit, a driving component for driving the function component, and a drive component such as a transport roller for transporting the sheet at sides of the sheet finishing unit, thereby making the sheet finishing unit protrude laterally and increasing a width thereof. Further, it is necessary to provide a mechanism for removing the function component in the sheet finishing unit when a worn out part is replaced or maintenance is performed upon malfunction, thereby further increasing the width of the sheet finishing unit.
In view of the problems described above, a first object of the present invention is to provide an image forming apparatus having a compact size with small protrusions in which a sheet is discharged from an image forming unit in a direction same as a direction that the sheet is discharged from a sheet finishing unit and an image reading unit scans the sheet in a direction substantially perpendicular to the direction that the sheet is discharged.
A second object of the present invention is to provide an image forming apparatus in which it is easy to confirm a sheet stored on a discharge tray in the image forming unit or the sheet finishing unit arranged vertically from a same direction.
Further objects and advantages of the invention will be apparent from the following description of the invention.